1. Field of the Invention
The present invention relates to a lightweight, highly mobile and efficient apparatus for instantaneously producing a high volume of compacted, solid carbon dioxide (CO2) pellets. The apparatus utilizes liquid CO2 that is discharged through nozzles and expanded to reach a triple point condition in which solid, liquid and gaseous forms of CO2 can coexist and flash to a mixture of CO2 in a gaseous phase and particles of snow in a process well known in the art. The gaseous CO2 is discharged into atmosphere or recovered for converting back to liquid by a vacuum recovery system or for use in extinguishing fire. The snow particles are aggregated into larger snowflakes which are compressed into pellets by an eccentrically supported rotor having radially movable vanes or blades mounted in radial slots in the rotor. The rotor and blades form circumferentially moving pockets associated with the interior surface of a partial rotor housing to compress the flakes into pellets as the volume of the pockets reduce as the rotor and blades rotate to a point of pellet discharge. The blades include slots extending to their outer edges which receive dividers rigidly mounted on the partial housing to divide the elongated pockets along the length of the rotor, housing and adjacent blades into smaller pockets to form smaller pellets. The smaller pellets are discharged from the partial rotor housing into an air lock which includes a housing and bladed rotor to convey the pellets to a discharge that is isolated from the pellet compression structure. The air lock includes an air discharge for the pellets to facilitate conveyance of the pellets to a point of use, such as the site of a fire in order to extinguish the fire.
2. Description of the Prior Art
The formation of CO2 pellets from CO2 snow is well known. Such pellets have been used for various purposes such as abrasive blasting when projected against a surface, conveying materials, neutralizing harmful substances in ambient air, quick freezing foods or other materials and the like.
The following U.S. patents disclose various uses of liquid CO2 including apparatuses to form CO2 pellets from liquid CO2.
U.S. Pat. No. 4,033,736
U.S. Pat. No. 4,389,820
U.S. Pat. No. 4,977,910
U.S. Pat. No. 5,355,962
U.S. Pat. No. 5,419,138
While certain of the prior patents disclose apparatuses for forming CO2 pellets, the operational characteristics including slow start up, low production volume and structural details including large heavy components and power requirements for operation have restricted the use of CO2 pellets for various uses.
For example, in U.S. Pat. No. 4,033,736, the impeller 80 is eccentrically mounted with respect to the housing 30. Snow is formed from liquid CO2 between the housing and impeller. When the impeller rotates, the snow is displaced radially through the extrusion passageways 52 in which the snow is compacted essentially by the reaction of springs 76. In the present invention, the snow is compressed as it moves circumferentially between the rotor and the housing in the pockets formed by the housing, rotor and radially movable blades on the rotor as the pockets move circumferentially and reduce in volume due to the eccentric relationship of the rotor and housing.
U.S. Pat. No. 5,419,138 discloses the use of a hydraulic ram to compact CO2 snow into pellets and discusses the development of prior apparatuses for producing CO2 pellets and snow, the uses of such pellets and snow and the operational parameters of the prior art. The production volume of the apparatus is low and the start up time is long. Also, the structure is heavy and requires substantial power to operate.
In contrast, the apparatus of the present invention provides instantaneous, high volume production of high density solid CO2 pellets and requires a small power input to produce pellets xe2x80x9con the spotxe2x80x9d where such pellets are desired to suppress fires, reduce pollution and other various uses.
Gaseous carbon dioxide with or without snow particles has been used to suppress fires, especially under certain hazardous conditions, for many years. Until the development of halon systems, CO2 was the only gaseous fire suppressant to effectively suppress fires of most materials with the exception of certain active metals and material containing their own oxygen source. Gaseous carbon dioxide is a desirable fire suppressant since it is not combustible, does not produce its own products of decomposition, provides its own pressurization for discharge from a storage container thereby eliminating the need for additional pressurization, leaves no residue thereby precluding the need of agent cleanup, relatively nonreactive with most materials, provides three dimensional protection because it is a gas under ambient conditions, is electrically nonconductive and can be used in the presence of energized electrical equipment. However, the use of gaseous CO2 has been somewhat restricted as a fire suppressant or extinguisher due to the inability of delivering gaseous CO2 to the site of a fire for distances much greater than 10 to 15 feet. Also, prior art devices do not produce sufficiently high volumes of CO2 pellets that can be delivered long distances to effectively fight fires and pollution.
Halon based systems are being phased out due to regulations of the Environmental Protection Agency (EPA) mandating phase out of ozone depleting substances. Carbon dioxide is considered an alternative technology and this invention provides for the use of CO2 as a replacement for halon and other ozone depleting substances which may harm the environment such as various foaming agents and the like.
It is an object of the present invention to provide an apparatus for instantaneously producing a high volume of high density solid carbon dioxide pellets from pressurized liquid carbon dioxide utilizing a relatively small, lightweight structure which is highly mobile. One embodiment of the invention has a total weight less than approximately 100 pounds, a height of approximately 30 inches and a depth and width of approximately 6 to 12 inches and powered by a small horsepower electric motor. The above dimensions may vary depending on the output desired. Alternatively, the unit can be powered by a gasoline or diesel powered engine of small horsepower. The above embodiment is capable of producing about 600 to 800 pounds of CO2 pellets per hour depending upon the size of the components and the rotational speed of a rotor. The apparatus has a startup time of approximately 3 seconds thereby providing a very effective and inexpensive and rapidly activated fire suppressant system.
Another object of the invention is to provide an apparatus for producing carbon dioxide pellets in accordance with the present invention and the preceding object which includes a manifold receiving pressurized liquid carbon dioxide that is discharged through a plurality of nozzles into square expansion tubes in which the liquid carbon dioxide is transformed into a mixture of gaseous carbon dioxide and snow particles. The gaseous carbon dioxide is vented to atmosphere or discharged into a vapor recovery system. The snow particles formed in the tubes by the expanding CO2 are aggregated in the pockets of a rotor system and compressed into solid carbon dioxide pellets.
A further object of the invention is to provide an apparatus for producing solid carbon dioxide pellets in accordance with the preceding objects in which the structure for compressing aggregated snow particles into pellets includes a partial generally cylindrical housing having a cylindrical rotor journalled therein with the rotational axis of the rotor being eccentric to the center of curvature of the partial cylindrical housing. The rotor includes radial slots receiving radially moveable vanes or blades having outer edges which are maintained in close contact with the interior of the partial cylindrical housing to form a plurality of closed pockets except for slots in the blades which receive arcuate dividers on the housing. The blades move radially in relation to the rotor as it rotates and moves the blades along the inner surface of the partial cylindrical housing to displace the snow particles and flakes circumferentially into a solid carbon dioxide pellet as the closed pockets formed by the housing, rotor and blades move from an inlet large volume to an outlet small volume. The dividers on the housing cut the pellet formed in each pocket into a plurality of smaller pellets which are discharged from the rotor.
An additional object of the invention is to provide an apparatus in accordance with the preceding object in which CO2 is introduced into the compressor through a nozzle in either side wall or both side walls with the nozzle including an orifice to enable expansion of liquid CO2 to its triple point.
A still further object of the invention is to provide an apparatus for producing carbon dioxide pellets as defined in the preceding objects in which a front wall is disposed in opposed relation to the partial cylindrical housing and includes projecting fins which are received in the blade slots to prevent snow particles from falling downwardly past the rotor and front wall. The apparatus also includes a source of pressurized air associated with the pockets as they move past the divider ends to assure removal of compressed solid pellets from the pockets.
Still another object of the invention is to provide an apparatus for producing carbon dioxide pellets in accordance with the preceding objects in which the smaller pellets are discharged from the rotor into an airlock for receiving the solid pellets. The airlock includes a cylindrical housing having a pellet inlet and a rotor with radial blades extending from the rotor into continuous engagement with the interior surface of the housing. The rotor and blades rotate about an axis concentric with the axis of the cylindrical housing and form a plurality of pockets having a constant volume. The housing includes a pellet outlet remote from the pellet inlet and also includes an air flow inlet and outlet which communicate with opposite ends of the airlock housing. Air flow through the housing entrains the solid carbon dioxide pellets and conveys the pellets from the airlock to a point of use or storage.
Another additional object of the invention is to provide an apparatus for producing CO2 pellets in which pellets are discharged from a pellet compressor by gravity and liquid CO2 is expanded in a tube discharging snow into pockets in the compressor with CO2 gas being collected for subsequent use.
Still another additional object of the present invention is to provide an apparatus in accordance with the preceding objects in which the compressor rotor rotates about a central axis and the compressor has an eccentric interior cooperating with the rotor and blades to compress CO2 snow into pellets.
Yet another very important object of the invention is to provide an apparatus for producing carbon dioxide pellets which is light in weight, small in overall size, capable of being transported easily, inexpensive to manufacture and operate, capable of easy and rapid startup and operation and capable of producing a high volume of carbon dioxide pellets for effective use for suppressing fires or for other uses.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.